Use "TypeBase::hasError()" rather than "is<ErrorType>()" where needed.

In most places where we were checking "is<ErrorType>()", we now mean
"any error occurred". The few exceptions are in associated type
inference, code completion, and expression diagnostics, where we might
still work with partial errors.

lib/Sema/ConstraintSystem.cpp

@@ -1326,7 +1326,7 @@ ConstraintSystem::getTypeOfMemberReference(
       if (!isClassBoundExistential &&
           !selfTy->hasReferenceSemantics() &&
           baseTy->is<LValueType>() &&
-          !selfTy->is<ErrorType>())
+          !selfTy->hasError())
         selfTy = InOutType::get(selfTy);
 
       openedType = FunctionType::get(selfTy, openedType);